Question
HI! I recently read online that the perfect soil combination is 1/3 part Peat Moss,1/3 part compost, and 1/3 part Vermiculite. What my question is, is should I add Osmocote to that as well to have a beautiful arrangement of flowers and plants in the bed outdoors or would that be over fertilizing? --Robin, Colorado Springs, Co

Answer
The combination you describe would provide for a very good container planting mix. It is very nice and loose and will ensure good drainage while at the same time provide just the right porosity for making water available to the plants and keeping fertilizer nutrients available.

For plants which require better drainage (begonias, caladium, dahlias, even ferns) you could consider substituting with perlite instead of vermiculite. This may also be easier to find in garden centers.

e.g. 1/3 peatmoss sphagnum, 1/3 compost or potting soil, 1/3 perlite.

However, there is no reason to go about amending the garden soil in this manner. The above recipies are excellent for containers, but for gardens this is not necerssary.

Simply add a 2-3" layer of compost and mix it into the top 8-10" of soil by turning it well into the soil. I use a shovel and dig up one shovels deep (about 10") and mix the soil with the 2-3" layer of compost. This makes the soil slightly raised (which is good for plants, too) and the compost aerates the soil. This provides for a 20-25% mix of compost and 75-80% native garden soil.

There is no reason to start hauling away garden soil or removing it. Most new gardeners believe that their garden soil is not very good and should be replaced. Nothing could be further from the truth. However, most kind of native garden soils can benefit from being improved. e.g. Amended into perfect planting soil mix by adding a 2-3" layer of compost and mixing with thorougly into the top 8-10" of native soil.

Note: Compost will have some nutrients already and can support most perennials, annuals etc for a short period of time, but then you should fertilize.

I think it is a good idea to add OSMOCOTE to most platings in addition to the compost, unless the plants you use do not require very much fertilizer.

Most flowers today are hybrid plants bred for improve flowering. They require more fertilizer than old species plants. Therefore, most plants typically do well with osmocote added in addition to compost.